Rolling Heat Research Articles

Effect of precipitation and solution behavior of impurities on mechanical properties of low activation vanadium alloy

Since vanadium alloys work harden during rolling to produce plate and such processing results in anisotropic mechanical properties, a post rolling heat treatment is required to recover the material properties. The effect of heat treatment temperature on mechanical properties was investigated and it was confirmed that heat treatment at 1073 K would recover the work hardening and provide better mechanical properties. In addition, the precipitation behavior of Ti–C–O was studied using solution heat treated plate to observe changes in the mechanical properties. Fine precipitates formed in high density at 973 K, increasing the yield stress. At 1173 K, larger precipitates formed at low density which decreased the yield stress. The 1373 K heat treatment dissolved all precipitates and resulted in a higher yield stress than that at 1173 K.

Changing the geometry of water spray on milling work roll and its effect on work roll temperature

An important parameter in the operation of hot rolling mill is the cooling mechanism of work roll. The determination of the best geometry of the cooling system, therefore, plays an important role in obtaining the highest heat transfer coefficient and in avoiding lateral water splashes. Using the finite-difference method, a computer program was developed to solve the work roll heat transfer equations in the unsteady state with varying boundary conditions. In the boundary condition for water spray, parameters such as spray angle, the angle of spray impact on work roll, the distance of header from work roll, water pressure, type of nozzle used, etc. are variable. This paper explains the effect of each one of these parameters on work roll temperature.

Formability of Magnesium Alloy Sheets Manufactured by Semi-Solid Roll Strip Casting

An experimental investigation was performed into the formability of magnesium alloy sheets that were hot-rolled after a semi-solid roll strip casting process. Semi-solid forming helps reduce the total product weight if the semi-solid material produced by light metals, such as aluminum and magnesium can be used to replace conventional iron and steel products. However, the problems of utilizing magnesium alloys are still related to high manufacturing costs. This means that improved quality must be balanced by economic validity. Magnesium alloy AZ31B was used in this experiment to ascertain the effectiveness of semi-solid roll strip casting for producing magnesium alloy sheets. The temperature of the molten magnesium, and the roll speeds of the upper and lower rolls, (which could be changed independently), were varied to find an appropriate manufacturing condition. Rolling conditions and heat treatment were changed to examine which condition would be appropriate for producing wrought magnesium alloys with good formability. Microscopic observation of the crystals of the finished products was performed. It has been found that a limiting drawing ratio of 2.4 was possible in a deep drawing process of the cast magnesium alloy sheets.

VAPOR FLOW ANALYSIS IN PARTIALLY-HEATED CONCENTRIC ANNULAR HEAT PIPES

The steady-state laminar and incompressible vapor flow in four partially-heated concentric annular heat pipe (CAHP) is studied. The governing equations are solved numerically, using finite volume approach based on collocated grids. The first order upwind scheme and the QUICK scheme are used in the numerical solution. The vapor pressure distributions and velocity profiles along the annular vapor space are predicted for a number of test cases in the range of low to moderate radial Reynolds numbers. The results show that in a partially-heated annular heat pipe, as the radial Reynolds number increases, a number of recirculation zones may be created at both ends of the evaporator and condenser sections. The size and location of the recirculation zones are predicted and their effects on the performance of an annular heat pipe are discussed qualitatively.

Texture development of a multi-filamentary Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ tape during thermo-mechanical treatment

In order to investigate texture development of superconducting grains, multi-filamentary Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ (Bi-2223)/Ag tapes were fabricated with different pass reduction ratios of rolling. The deformation-induced-texture and reaction-induced-texture for Bi-2212 and Bi-2223 were evaluated by X-ray diffraction including pole figure analysis. It was found that the texture of Bi-2223 develops by the progress of thermo-mechanical treatment. The texture for both Bi-2212 and Bi-2223 was found to develop better along the rolling direction than the transverse direction. By scanning electron microscopy observation, the highly textured region of Bi-2223 grain was found to expand by the intermediate rolling and additional heat treatment.

Continuous Heating System Using Electric Resistance Heating for the Hot Rolling of Stainless Steels.

Electric resistance of metals increases according to the elevation in temperature. Non-uniform temperature distribution in cross-section can be automatically sacrificed if we use electric resistance heating, and uniformly distributed cross-sectional temperature can be easily obtained. A continuous heating system using electronic resistance heating is developed, and its characteristics to the heating of stainless steel are examined through a series of basic experiments. Through the investigation, it has become clear that uniform continuous heating of stainless steel can be realized by proposed heating system. Although the composition of heating system is quite simple, high rate in temperature elevation can be obtained. Also, we can precisely control the temperature distribution in feeding (rolling) direction by continuous electric resistance heating, because temperature of metals can be rapidly changed only by changing the degree of electric current and time to impose electric current.

Applications of Robot Technology to the Paper Making Industry

Marol Co., Ltd.; well known for the manufacturer of Marol Brand hydraulic steering systems, autopilot and engine remote control systems for marine use, also designs and manufactures special purpose robots for industrial use. The company introduces three of their custom applications for the paper making industry.(1) Palletizing Robot for Handling Carbon-less Duplicating Paper RollsThis was developed to grip the outside of the roll efficiently without any transference and to handle rolls of different sizes and weights at random.(2) Custom Designed Automatic Grinder/Cleaner for Backing Roll of Existing CoaterThis was developed to clean the surface and remove scratches from Backing Roll. The device can be operated during operation and the surface of the roll can be kept clean as required. The device has functional flexibility so it can be operated under various conditions.(3) Custom Designed Automatic Grinder/Cleaner for Heat Roll of Existing Soft CalendarResearching various materials led to the development of this grinder that can withstand heat and grind the roll to remove contaminant and finish the roll to the required surface roughness. The device can be operated during operation and the surface of the roll can be kept clean as required. The device has functional flexibility so it can be operated under various conditions.

Heat Transfer and Roll Surface Temperature in the Hot Rolling of Aluminum Sheet

Roll surface temperature in the arc of contact has been directly measured by a temperature sensor embedded on the roll surface during the hot rolling of aluminum sheet. Influences of the rolling parameters such as initial sheet temperature, reduction ratio, and lubrication condition on the roll surface temperature have been investigated. The roll surface temperature abnormally increases in the entrance part of the contacting arc when the rolled sheet seized on the roller with no lubricant. By comparison with the roll surface temperature simulated by one-dimensional finite difference method, the heat transfer coefficient between the roll and the sheet surfaces was estimated to be approximately 400 kW/m2K. A simulation of the abnormal increase in the roll surface temperature in the case of seizure has been performed by adding the heat generation in the surface layer of the sheet caused by friction on the boundary surface.

The effect of reduction ratio of hot rolling on texture and secondary recrystallization of MA 754 plate

Ni-base oxide-dispersion-strengthened (ODS) superalloys produced by a mechanical alloying process have been used for high temperature applications because of their excellent high temperature strength, which can be useful up to a relatively high fraction of their melting points [1]. The high temperature strength of ODS superalloys is attributed to the presence of finely dispersed inert oxide particles, which gives dispersion strengthening effect by acting as a barrier to dislocation motion [2]. In order to develop high temperature strength, fine grains should be transformed into elongated coarse grains, which contributes to the retardation of the creep process and thus the prolongation of rupture life. The coarse elongated grains with a high grain aspect ratio (GAR), which is defined as the ratio of grain length (L) to grain width (W ), are possible with a high temperature annealing, during which secondary recrystallization occurs [3–6]. In particular, INCONEL alloy MA 754, which has been used as a turbine vane material in advanced jet engines, obtains the desired grain structure by isothermal annealing [7]. Although the exact mechanism of secondary recrystallization behavior is not fully understood yet, the importance of GAR has received considerable attention [3, 6, 8]. The general aim of thermomechanical processing (TMP) of ODS superalloys is to achieve a coarse grain morphology by means of secondary recrystallization [8, 9]. Another purpose of TMP is to increase the availability of the necessary product forms. However, subsequent secondary recrystallization behavior strongly depends on the temperature, strain rate, and strain of the prior TMP operation and also such compositional factors as yttria content and the amount of excess oxygen [10]. Bieler et al. have reported that the temperature and strain history during hot working have a large effect on texture, even though the same final sheet thickness was reached [11]. In a recrystallization study on a similar alloy, the recrystallization texture of sheet was sensitive to the heat treatment and rolling history [12].

Superelastic Shape Memory Alloy For Seal Applications Produced by Low Pressure Thermal Spray Technology

AbstractThe objective of this development program was to demonstrate the feasibility of producing superelastic NiTi shape-memory alloy (SMA) foil material by the low pressure plasma spraying (LPPS) process for the development of robust, corrosion resistant and long life sealing technology.A conventional LPPS facility was retooled for the use of electric wire arc spraying and the process parameters were reconfigured. Foil specimens sprayed up to 1.5mm thickness showed good ductility after consolidation heat treatment at 950'C for 1 hour. Subsequent rolling of the foil specimens to a thickness of 0.5mm exhibited superelastic behavior. The amount of superelasticity will have to be determined. In addition, thin (0.2 mm) and thick (0.76mm) wall tubes have been produced in the 12.5mm diameter range. These samples were heat treated and subjected to Hot Isostatic Pressing (HIP). Metallographic examination revealed dense, solid microstructures after heat treatment and rolling, and hot isostatic pressing respectively.It was concluded, that this development established the feasibility to produce near net shape superelastic NiTi foil with a retooled Low Pressure Wire Arc Spraying (LPWAS) process, modified to permit substitution of NiTi-wire for NiTi-powder as feed stock.

加熱小型ダイスによる高性能ＧＦＲＴＰねじの転造

A new form rolling technique to produce high performance GFRTP (glass fiber reinforced thermo plastic) thread by heating mini die is developed. GFRTP is widely used due to its superior properties, such as high strength, lightweightness, corrosion resistance and electrical insulation. Thus, the high performance GFRTP fastner is desired in various industrial fields. The form rolling is a standard technique for metal threads. It is supposed that the form rolling of GFRTP rods, in which the glass fibers are arranged along the axis of rods, makes possible for fiber to flow into threads during form rolling period, and the cost effective high performance GFRTP bolts would be available. In order to obtain precise thread shape and high strength, it is considered that the material temperature should be higher than the glass transition temperature and ultrasonic heating has been applied in form rolling process. However, sufficient thread shape could not be obtained, because the high temperature of the inner part causes total material deformation and the forming pressure becomes small. To cope with this problem, a new heating mini die is designed to apply local heating and large local form rolling pressure. It is found that the precise thread shape is achieved and the glass fibers flow into threads by the proposed heating mini die.

Effect of process variables on tensile properties of ingot processed versus strip cast iron aluminides

The effects of cold rolling and subsequent heat treatment are reported for ingot cast-hot rolled and strip cast iron aluminides (23–29 at.-%Al). Partially recrystallised microstructures obtained by hot rolling at 800°C gave higher strength and elongation to fracture than hot rolling at 1000° C. Elongation increased and proof strength decreased in proceeding from DO3 to mixed B2 + DO3 and to B2 order as a result of heat treatment following cold rolling. Variability in the properties of strip cast material was associated with casting defects such as laps, but the best properties were comparable with those of ingot processed material. The detrimental effects of tensile specimen preparation by spark erosion are discussed.

Special features of the formation of microstructure of heat-treated low-alloy steel

The strength and the operational properties of low-alloy thick-sheet steels is increased by heat treatment in the line of the mill with the use of the rolling or furnace heat. The present work concerns the special features of structure formation and the mechanical properties of rolled stock from sheet structural steel 09G2S with a strength level C345 (σy=325-345 MPa) in a hot-rolled and a normalized state after accelerated cooling from the normalizing furnace and after rolling behind the finishing stand. As a result of the rapid cooling in the line of the mill the sheet acquires properties corresponding to steels with a C390–C440 strength level (σy=390-440 MPa).

Structure and properties of heat-treatable steels for metallic constructions

In order to substantiate the choice of the temperature of heat or combined treatment with the use of rolling heat or with individual heating, it is expedient to determine the temperature dependence of the grain size of the steel. The present work concerns the effect of the temperature of heating for rolling on the structure and properties of low-carbon (VSt3ps) and low-alloy (09G2S, 09G2FB, 16G2AF, 15G2AFDps, 14Kh2GMR) building steels. In order to bring the structure of the specimens into correspondence with the structure of slabs slowly cooled in air after rolling the ingots under the conditions of a metallurgical plant, the preforms were subjected to a preparatory heat treatment. The temperature dependences of the grain size of austenite and the mechanical properties of the steels are presented.

An asymptotic model of work roll heat transfer in strip rolling

An asymptotic model of work roll heat transfer is developed using a multiple time scale approach. The model is appropriate under typical high Peclet number rolling conditions and provides a unified framework for relating previous roll heat transfer models. The solution consists of a fast time scale thermal boundary layer near the roll surface, along with a slow time scale core heat transfer problem. Several features of the model are illustrated. First, boundary layer behavior is examined under steady and dynamic conditions. Here, the decay rate for boundary layer transients is determined and theoretical steady-state temperature distributions are compared against previously reported experimental data. Heat transfer within the core is then considered under relatively general surface heating conditions. In the special case where the surface heat flux is constant, core temperatures are shown to increase linearly with time. In the last illustration, the model is used to obtain inverse estimates of circumferentially varying roll surface heat flux and temperature distributions. In this case, comparisons are made with the finite difference-based inverse estimates recently reported by Huang et al., International Journal of Heat and Mass Transfer, 1995, 38, 1019–1031.

誘導発熱ジャケットロール 製紙における高温カレンダロールの展開

An induction heated jacket roll is regarded as an ideal heat roll, which gives uniform surface temperature with a good CD profile.Traditional heat rolls which use heated thermal medium produce uneven temperature profiles and cause higher temperature at the both ends of the rolls. This results in variation in a roll diameter CD profile and finally results in sheet thickness variation.The roll of this paper has an induction heat device inside and is jacketed like a heated pipe. With the combined effect by them, the temperature variation in a radial direction is compensated and the roll CD diameter profile is very well stabilized.Now, super soft calender rolls with a max. temperature of 360 degree C are successfully in operation.

Microstructure of Ag/Bi(Pb)-2223 Tapes Prepared by Solid-State Reaction

The processing of Ag/Bi(Pb)-2223 tapes via the prevailing solid state reaction was investigated. A precursor powder of the composition Bi1.86Pb0.26Sr1.96Ca1.95Cu2.97O10+δ containing mainly Bi-2223 phase was employed. Particular attention was devoted to the microstructural properties of the tapes subjected to rolling and subsequent heat treatment in one, two, and three steps, respectively. A sharp texturing gradient exists in the superconducting cores, and the repeated treatment leads to deterioration of the superconducting properties. The latter effect is ascribed to the formation of periodic defects arising during the repeated rolling of the sintered superconducting core.

Experimental investigation of the mechanical properties of quenched rails for different quenching conditions using the temperature directly from rolling heating

Because of increasing rail traffic in conjunction with the application of greater axle loads, there is need to provide higher strength steel rail. Quenching treatment along the whole steel rail, directly using the temperature from the rolling heating, has been employed in the rolling line. Six different quenching conditions were used, from 720 to 840 °C, in order to seek the optimum heat-treatment schedules of the steel rails. The microstructure and mechanical properties of the quenched steel rails were investigated. The test results show that the conventional mechanical behaviour of the quenched rails surpasses the West Europe Standard: σ 0.2740MPa, σ b 1160MPa, σ 59%. The hardness distribution over the cross-section of the quenched rails uniform, the hardness difference along the longitudinal section of the quenched rails being ΔH b < 30. When the quenching temperature is 740 °C, a quenched steel rail with the best mechanical properties and with small pearlite nodules can be obtained.

Determination of strand surface temperature and heat transfer during continuous casting

The embedded thermocouple technique for measuring strand surface temperatures has been developed and used to measure temperatures on British Steel casters. Mathematical modelling methods have been developed to derive from these measurements information on spray heat transfer, roll heat extraction and heat transfer from surplus spray water in the gaps between rolls and sprays. The analysis uses an inverse solidification model.

Deformation and microstructure development during hot-pack rolling of a near-gamma titanium aluminide alloy

Deformation behavior and microstructure development during hot pack rolling of the near-gamma titanium aluminide alloy Ti-45.5Al-2Cr-2Nb (atomic percent) were established. Deformation behavior was investigated through rolling at various nominal furnace temperatures and parallel modeling studies using a finite difference approach to predict temperature transients during workpiece transfer from the furnace and during the rolling operation itself. Agreement between measured rolling pressures and predictions based on a rule-of-mixtures (ROM) average of the flow stresses of the pack components (at the predicted temperatures and strain rates within the roll gap) was excellent. As-rolled microstructures were interpreted in terms of the Ti-xAl-2Cr-2Nb pseudobinary phase diagram, predicted temperature transients during rolling, and the static (no deformation) phase-transformation behavior of the program material. These results demonstrated the strong influence of furnace preheat temperature on microstructure development, as well as the tendency for temperature transients due to radiation heat losses and roll chilling to suppress phase transformations.